Thumb guard



FIG. 1 is a front elevational view of a thumb guard showing my new design;

FIG. 2 is a side elevational view;

FIG. 3 is a rear elevational view;

FIG. 4 is a top plan view; and

FIG. 5 is a reduced perspective view thereof, the broken line showings being for illustrative purposes only. 

The ornamental design for a thumb guard, substantially as shown and described. 